Catheters are commonly used invasively to treat diseased vessels in mammalian, and particularly human, bodies. Cardiovascular diseases are one of the most common diseases treated in this fashion, wherein the catheters are used to counter atherosclerosis through such angioplasty treatment modalities as balloon angioplasty. Other uses include: treatment of the urinary tract, brain, lungs, kidneys and/or liver. Such angioplasty treatments of body vessels can include laser cutting, dilation, tissue heating, chemical dissolution of tissues and/or removal of tissue samples.
In some of these treatments, it is contraindicated to have a long-term blockage, that is, one occurring for more than approximately 30-60 seconds. In addition, certain heart-attach victims may have enough necrotic heart tissue that no interruption of blood flow can be safely tolerated. For this reason, perfusion catheters have been constructed which are adapted to pass blood through the catheter even though the catheter is acting to block flow externally of the catheter. That is, balloons are commonly used to dilate partially blocked arteries and veins to restore more normal blood flow. It has been found that the dilation is more effective if prolonged; yet this usually means a prolonged blockage of flow around the catheter since the balloon of the catheter fills the body vessel.
Conventional perfusion catheters have one or more simple apertures upstream of the blockage site, and one or more downstream. See for example, U.S. Pat. No. 4,581,017, FIG. 2. Such catheters have a rate of flow-through that is primarily controlled by the diameter of the flow lumens within the catheter and the pressure difference across the lumens. The magnitude of that rate does not usually provide the high fluid flow rate required of that body vessel. As a result, treatments requiring a more extended blockage are risky, since even with the perfusion provided, the flow downstream of the catheter is not equal to natural flow.
In dealing with the aforesaid problem, pumps have been hooked up to perfusion catheters. However, as shown for example in U.S. Pat. No. 4,666,426, the approach has been to withdraw blood from apertures at an upstream location, deliver it to the pump itself and to processing stations located ex vivo, and then return it to the catheter to be expelled back into the body vessel at apertures located downstream of the intake apertures. Such an arrangement requires the blood to run the complete circuit, including ex vivo stations. This creates the following problems:
(1) There is greater risk of contamination to the patient as well as attendants, since blood contactable objects are not confined with the body.
(2) Such a system is more likely to lyse blood cells due to the greater exposure to potentially "unnaturally high" fluid shear stresses encountered within the pumping system.
(3) The pumping system is not entirely disposable. The parts not disposable must be cleaned, which is an expense that should be avoided.
Thus, a first problem prior to this invention has been to provide a higher throughput of body fluids in a perfusion catheter, so as to allow a more prolonged obstruction of the vessel carrying the fluid, by the catheter.
A second problem prior to the invention has been to provide a perfusion catheter and pump arrangement wherein the blood or other body fluid is drawn into the catheter, bypassing the obstruction, and then immediately expelled under pressure, without undergoing an extensive ex vivo loop.